Pawl and ratchet mechanism



Patented July 13, 1954 PAWL AND RATCHET MECHANISM Graham S. McCloy,

to Westinghouse Pittsburgh, Pa., a

Original application Febru 143,788, now Patent No 6, 1952. Divided and this ber 10, 1951, Serial No.

3 Claims.

This invention relates to pawl and ratchet mechanisms and is a division of my copending application, Serial No. 143,788, filed February 11, 1950, now Patent #2,595,967 for an improvement in refrigeration apparatus.

The'invention more particularly relates to improved ratchet and pawl mechanisms for counting devices such as might be used in an automatic defrosting control for refrigerators, which control initiates defrosting after the refrigerator door has been opened and closed a predetermined number of times. Controls of this type may employ a ratchet wheel which is advanced bythe opening and closing of the refrigerator door. When this wheel completes one revolution it engages and moves a control member into position to energize the defrosting apparatus.

It is an object of the invention to provide novel means for actuating a ratchet wheel.

It is another object of the invention to provide a novel pawl arrangement for converting reciprocating motion of a plunger into rotary movement of a ratchet wheel.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a View of a control mechanism having the cover thereof removed and including a pawl and ratchet mechanism constructed and arranged in accordance with the invention;

Fig. 2 is a sectional view of the control mechanlsm shown in Fig. 1 and is taken along the line IIII of Fig. 1; and

Fig. 3 is a slightly enlarged View in perspective of the movable pawl and dog of the mechanism shown in Figs. 1 and 2. 7

Referring to the drawings wherein I have shown my invention as applied to a switch-actuating mechanism such as might be employed for energizing the defrosting apparatus of a domestic refrigerator, the numeral l6 designates a plunger having a rectangular portion ll which projects into a housing I 8 and slides in a rectangular groove therein. When used as a defrost control the casing l8 may be so positioned within the refrigerator cabinet that the plunger is moved inwardly of the casing (upwardly as viewed in Figs. 1 and 2) each time the refrigerator door is closed. When the door is again opened, a spring 50 positioned within the casing I8 moves the plunger I 6 outwardly,

A toothed ratchet wheel 22 is journaled on a fixed portion 24 (best shown in Fig. 2) of'the Springfield, Mass., assignor Electric Corporation, East corporation of Pennsylvania ary 11, 1950, Serial No.

2,595,967, dated May application Septemhousing 5 8. A U-shape spring element 26, cut from flat sheet material, is secured to the housing 18 by means of a screw 28. One leg 30 of the spring element 26 overlies the ratchet wheel 22 to retain the latter on the portion 24 of the housing 18. The other leg 32 overlies the ratchet wheel 22 and is preferably spaced axially from the end of a pin 34 in the position of the apparatus shown in Fig. 2. The pin 34 is slidably supported for axial movement within the fixed portion 24 of the housing iii.

A spring 35, formed of sheet material and best shown in Figs. 1 and 3, comprises a generally L- shaped actuating pawl 36. One leg 38 of this pawl 38 is suitably secured at its lower end to the housing H3. The upper end of the leg 38 includes a portion 39 which is bowed to the right as viewed in Fig. 1. The other leg 40 of the L-shaped actuating pawl 33 extends horizontally to the left. The free end of the leg 40 is notched at 42 and rides on the ratchet wheel 22 to engage a tooth on the periphery thereof.

The sliding element or plunger 16 has a depression 44 including an inclined face 46 formed in the portion l1 thereof. The bowed-out portion 39 of the actuating pawl 38 is biased by the leg 33 into the depression 44, and as the plunger [6 is moved upwardly, as seen in Figs. 1 and 2, the inclined face 46 engages the bowed-out portion 39 of the actuating pawl 36 and moves it together with the leg 48 to the left as viewed in Fig. 1. This leftward movement of the leg 4!] advances the ratchet wheel 22 in a counterclockwise direction. The spring 35 also comprises a dog 48, which also engages a tooth of the ratchet Wheel 22 and prevents clockwise rotation thereof.

When the force acting on plunger 16 is removed, the plunger moves downwardly as viewed in Fig. 2 under the action of spring 50 so that the bowed-out portion 39 of the actuating pawl 36 together with the leg dd moves to the right and into the depression 46. The leg 43 is resilient so that the free end of the leg 43 rides over one or more teeth of the ratchet wheel 22 to engage an adjacent tooth.

It will be observed that the bowed portion 39 of the actuating pawl 3'6 forms a follower for the cam surface 49 of the plunger Hi. It is biased against the cam surface 33 by the leg 33 which is relatively straight to afford stiffness against vertical movement of the bowed portion 33 as viewed in Fig. 1. The leg it lies substantially tangentially to the ratchet wheel 22 to afford stiffness to insure transmission of the movement of the bowed portion 39 to the teeth of the ratchet wheel a b 22. The tangential position of the leg 40 also affords resilience to the movement of the free end of the leg 4t radially of the wheel 22 which movement allows the free end of the leg 40 to ride over the teeth of the ratchet wheel 22.

The ratchet wheel 22 carries an arcuate wed ing cam 52 which is gradually forced under the leg 32 of the spring element 26 as the wheel 22 revolves and flexes the leg 32 awayfrom the sliding pin 3G. Upon further movement of the ratchet wheel 22 in the counterclockwise direction, the cam 52 releases the leg iifiwhich, due to its resiliency, swings back to'its illustrated. position and then, because of itsinertia, swings beyond this position to drive the-pin 3% to the'left. The leg 32, being resilient, thereafter'returns to its illustrated position.

A snap-acting switch element 54 is secured at its lower end in the casing It by a bolt The element 3 comprises a switch blade 53 formed of fiat spring material. The blade 58 has 'an inverted U-shaped extending tongue 6'; in the center of the blade 58. A C-shaped compression spring Ed is interposed between the top of the tongue t2 and the upper edge of the slot The spring 6 t biases the upper portion of the blade 53 away from the upper portion of the tongue Two double-faced contact buttons it are afiixed to the upper end of the switch blade sets of contact fingers and it are secured in the upper portion of the casing it by bolts 12 and M, respectively, which bolts also form binding posts for electric conductors. The contact fingers i3 and iii are so disposed that when the Switchblade is in the left-hand position as viewed in Fig. 2, the two contact fingers it are bridged and when the switch blade 55 is in the right hand position, the two contact fingers it are bridged. Also, if the tongue 62 is moved to the left-hand position, as viewed Fig. 2, the switch blade 58 snaps to the right-hand position and if the tongue 62 is then moved to the right-hand position, the switch blade 53 will snap to the lefthandposition.

The tongue 62 is positioned adjacent the pin 65 so that when the latter is struck by the leg 32 of the springelement 26 and the tongue 2,2 is in the right-hand position, it will be moved to the left-hand position under the impact of the pin 34. The bridging of the contacts 68 which results, be used to energize suitable apparatus to eftect defrosting of a refrigerator.

When the defrosting oi the refrigerator is complete, the switch blade 58 must again be moved to its left-hand position or the position illustrated in the drawing, wherein normal operation of the refrigerating apparatus is effected. Fo this purpose a second pin '53 is positioned to the left of the tongue E2. The pin is moved to theright, as viewed in Fig. 3, by a flexible metal bellows 85) which forms one wall of the vessel 82. The vessel 82 communicates with a tube a l and is preferably filled with a volatile fluid whose pressure varies with the temperature of the refrigerating apparatus. The movement of the pin '58 is opposed by a spring be, one end of which engages the head 88 of the pin l8 and the other end of which engages the plate 538, the positi 1 of which may be adjusted by a screw 92. It be understood that when the pressure of the volatile fluid acting on the bellows is increased to a predetermined. value at which complete deirosting or" the refrigerator is carried out, the pin it will be moved to the right sufficiently to force the tongue 62 to slot 6t defining an upwardly,

Two

the position illustrated in Fig. 2. Accordingly, the contacts 68 are moved out of engagement with the fixed contact 68 and into engagement with the fixed contact 10 for again initiating the refrigerating cycle.

From the foregoing it will be apparent that I have provided a novel ratchet and pawl mechanism capable of transforming reciprocating motion into rotary motion. It is to be understood that I have shown and described my invention as applied to a-door-operated, refrigerator defrosting control merelyfor the purpose of illustratin a preferred embodiment thereof and that the invention can be embodied in apparatus other than that shown'and. described. For example, the particular switch-actuating mechanism shown forms no part of the present invention, but is claimed in my copending application referred to above and of which the present invention is a division. Hence, the ratchet wheel 22 might be employed to actuate a rotary switch directly-rather than the mechanism shown. Furthermore, the plunger [6 might be "actuated "by the movement or any element or machine when it is desired to count the operations or" such element or machine. In such an application the ratchet wheel 22 could likewise be connected to an indicator for the purpose of indicating the number of operations of the element or machine.

While I have shown-my invention in but one form, it will be obvious to those skilled inthe art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What I claim is:

l. The combination with a toothed ratchet wheel, of a pawl for actuating said wheel, said pawl comprising a generally L-shaped spring membenhaving firstand'second legs said firstleg being stationarily secured at the extremity thereof, the free-end of said second leg engaging a tooth on said ratchet wheel, saidsecond leg lying substantially tangentially to said ratchet-wheel at the location of said tooth, said spring member further comprising a holding dog secured at one end to the stationary end-of said first leg, the free end of said dogiengaging a-second tooth on said ratchet wheel, and means engaging said pawl at substantially the junction of said first and second legs for moving .said second leg in said tangential direction to advance said ratchet wheel, said holding'dogpreventing reversemovemerit of said ratchet wheel'when said actuating pawl is released to ride backover'and engage another tooth of the ratchet wheel.

2. The combination with a toothed ratchet wheel of a unitary pawl and dog structure for actuating said wheel, said structure comprising agenerally L-shaped spring member having first and second legs, said first leg being stationarily secured at the extremitythereof, the freeend of said second leg-engagingatooth on-said ratchet wheel, said second 'leg lying substantially tangentially to said ratchet wheel at the location of said tooth,'said first leg of said spring member having a portionthereof struck out to form a dog for engaging a second tooth on said ratchet wheel, and means engaging said spring member at substantially the junctionof said first and second legs for moving the second leg'in said tangential direction to advance said ratchet Wheel, said dog preventing reverse -movement of said ratchet wheel when said second leg is released .to ride back over and engage another tooth of the ratchet wheel.

3. A pawl and ratchet mechanism comprising a. toothed ratchet wheel, a unitary pawl and dog structure for actuating said wheel, said structure comprising a generally L-shaped spring member having first and second legs, said first leg being stationarily secured at the extremity thereof, the free end of said second leg engaging a tooth on said ratchet wheel, said second leg lying substantially tangentially to said ratchet wheel at the location of said tooth, said spring member further comprising a holding dog positioned near the stationary end of said first leg, the free end of said dog engaging a second tooth on said ratchet wheel, and an actuating member arranged for reciprocating movement along a line substantially parallel to the first leg of said L-shaped member, said actuating member having a cam surface adapted to engage said L-shaped member at substantially the junction of said first and second legs to move said second leg in said tangential direction to advance said ratchet Wheel when said actuating member is moved in one direction, said holding dog preventing reverse movement of said ratchet Wheel when said actuating member is moved in the opposite direction to permit said second leg to ride back over and engage another tooth of the ratchet Wheel.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,651,558 Sheridan Dec. 6, 1927 1,656,134 Birkett Jan. 10, 1928 2,406,220 Hines Aug. 20, 1946 

